The majority of bacterial pathogens and opportunists colonize the mucosal surfaces of their hosts by expressing specific adhesins that bind to host target receptors. Many Escherichia coli urinary tract isolates, in particular those that cause kidney infections, contain multiple pyelonephritis-associated pili (pap) operons, each of which is capable of expressing and assembling cell surface fimbriae. Lrp is a regulatory protein that exerts global control over as many as 50 genes in E. coli. In some cases, such as ilvIH, fim switching, and pap pilin transcription, Lrp is a positive regulator. In other cases, such as sdaA, livJ, and livKHMGF, Lrp acts negatively. Analysis of mutations within pap regulatory DNA that allow transcription of pap in the absence of Papl indicates that Papl does not interact with pap DNA. The regulation of pap gene expression is complex and involves a variety of factors including Lrp, Dam, CRP, Papl, PapB, and possibly H-NS. In addition, RimJ, the N-terminal acetylase of ribosomal protein S5, may play a role in thermoregulation. As a member of the Lrp regulon, Pap fimbrial regulation is tied to cellular metabolism, although it is not leucine responsive. Under the CRP regulon, Pap fimbrial expression is shut down when rich carbon sources such as glucose are present.

Methy lation patterns of Pap phase on and phase off cells. The square at the upper left represents binding of Lrp-PapI around the GATC-I site, whereas the oval at the lower right represents binding of Lrp near the GATC-I site. Black dots indicate methyl groups covalently attached to adenosine residues by Dam.

10.1128/9781555818340/fig28-1_thmb.gif

10.1128/9781555818340/fig28-1.gif

Figure 1

Methy lation patterns of Pap phase on and phase off cells. The square at the upper left represents binding of Lrp-PapI around the GATC-I site, whereas the oval at the lower right represents binding of Lrp near the GATC-I site. Black dots indicate methyl groups covalently attached to adenosine residues by Dam.

Organization of the regulatory region of the pap operon. Binding domains for PapB (18), Lrp and Lrp-PapI (12, 42), and CRP (22) as well as the 27-bp inverted repeats containing GATC-I and GATC-II are shown as boxes. Also shown are the transcription start sites of the papl and papBA transcripts. PapB site 2 overlaps the -10 RNA polymerase recognition site at the papBAp promoter.

10.1128/9781555818340/fig28-2_thmb.gif

10.1128/9781555818340/fig28-2.gif

Figure 2

Organization of the regulatory region of the pap operon. Binding domains for PapB (18), Lrp and Lrp-PapI (12, 42), and CRP (22) as well as the 27-bp inverted repeats containing GATC-I and GATC-II are shown as boxes. Also shown are the transcription start sites of the papl and papBA transcripts. PapB site 2 overlaps the -10 RNA polymerase recognition site at the papBAp promoter.

Regulatory regions of four Lrp-regulated E. coli fimbrial operons. The organization of the pap (10), fae (29), pef (20), and fan (30, 49) fimbrial regulatory regions are shown. Genes sharing sequence similarities with papl are denoted by dark shading, whereas genes with sequence similarities to papB are denoted by diagonal stripes. DNA sequences with similarity to the pap GATC-I box (CGATCTTTTAT) and GATC-II box (AAGATCGT) (53) are depicted as small open boxes. Transcription start sites are shown by arrows. The insertion sequences within fae are not drawn to scale. In the pef operon, ORF 7 overlaps the 3' end of the pefI gene.

10.1128/9781555818340/fig28-3_thmb.gif

10.1128/9781555818340/fig28-3.gif

Figure 3

Regulatory regions of four Lrp-regulated E. coli fimbrial operons. The organization of the pap (10), fae (29), pef (20), and fan (30, 49) fimbrial regulatory regions are shown. Genes sharing sequence similarities with papl are denoted by dark shading, whereas genes with sequence similarities to papB are denoted by diagonal stripes. DNA sequences with similarity to the pap GATC-I box (CGATCTTTTAT) and GATC-II box (AAGATCGT) (53) are depicted as small open boxes. Transcription start sites are shown by arrows. The insertion sequences within fae are not drawn to scale. In the pef operon, ORF 7 overlaps the 3' end of the pefI gene.

Comparative amino acid analysis of PapI-related DNA sequences. The amino acid sequences of PapI (10), SfaC (25), PrsI (39), DaaF (3), PefI (21), and FaeA (29) are shown. Dashes represent gaps introduced for alignment purposes. On the top row, cons denotes total consensus at a given amino acid position among all six regulatory proteins. Amino acids that are conserved among all six PapI-like proteins are shown in boldface type. Lowercase letters indicate that at least three sequences contain the same amino acid at a single position. Boxed regions show identities between either PefI and DaaF or PefI and FaeA or identities among PefI, DaaF, and FaeA that are not present in PapI, SfaC, or PrsI sequences.

10.1128/9781555818340/fig28-4_thmb.gif

10.1128/9781555818340/fig28-4.gif

Figure 4

Comparative amino acid analysis of PapI-related DNA sequences. The amino acid sequences of PapI (10), SfaC (25), PrsI (39), DaaF (3), PefI (21), and FaeA (29) are shown. Dashes represent gaps introduced for alignment purposes. On the top row, cons denotes total consensus at a given amino acid position among all six regulatory proteins. Amino acids that are conserved among all six PapI-like proteins are shown in boldface type. Lowercase letters indicate that at least three sequences contain the same amino acid at a single position. Boxed regions show identities between either PefI and DaaF or PefI and FaeA or identities among PefI, DaaF, and FaeA that are not present in PapI, SfaC, or PrsI sequences.

Regulatory networks affecting the pap operon. Large circles represent the operons controlled within each regulatory network or regulon, and numbers denote the various classes of regulatory control. The operons pap, daa, and sfa are members of class 2 since they are controlled by Lrp, CRP, and DNA methylation patterns. The fan operon belongs to class 3 since it is not regulated by Dam. The mtl, cdd, flh, and gut operons (54) are possible members of class 1, although it is not known if any of these operons are regulated by Lrp or Dam. Finally, my colleagues and I (26) recently identified a gene located at 77 min on the E. coli chromosome; the gene contains a nonmethylated GATC site dependent on the presence of Lrp, possibly a member of class 4.

10.1128/9781555818340/fig28-5_thmb.gif

10.1128/9781555818340/fig28-5.gif

Figure 5

Regulatory networks affecting the pap operon. Large circles represent the operons controlled within each regulatory network or regulon, and numbers denote the various classes of regulatory control. The operons pap, daa, and sfa are members of class 2 since they are controlled by Lrp, CRP, and DNA methylation patterns. The fan operon belongs to class 3 since it is not regulated by Dam. The mtl, cdd, flh, and gut operons (54) are possible members of class 1, although it is not known if any of these operons are regulated by Lrp or Dam. Finally, my colleagues and I (26) recently identified a gene located at 77 min on the E. coli chromosome; the gene contains a nonmethylated GATC site dependent on the presence of Lrp, possibly a member of class 4.